1. Field of the Invention
The invention relates to a fuel pump for arrangement in a fuel tank for delivering fuel to an internal combustion engine of a motor vehicle, the fuel pump having a rotor with guide vanes rotatably arranged in a pump housing and part annular ducts arranged in the pump housing and bounding one ring of vane chambers to form delivery chambers leading from an inlet duct to an outlet duct, the delivery chambers having a further connection for supplying an ejector which delivers fuel within the fuel tank.
2. Description of the Related Art
Fuel pumps which simultaneously supply at least one ejector with fuel and deliver fuel to the internal combustion engine of the motor vehicle are frequently employed in present-day motor vehicles and are known from practice. The known fuel pumps have a single delivery chamber. Fuel is delivered through the delivery chamber to the outlet duct and to the connection leading to the ejector. A valve which opens above a specified pressure is arranged in the connection leading to the ejector. This ensures that, below the specified pressure, the entire portion of fuel delivered by the pump is directed to the internal combustion engine.
A disadvantageous feature of the known fuel pump is that the valve represents a cost-intensive component and is susceptible to fault. In addition, the quantity and pressure of the fuel delivered to the internal combustion engine fluctuates due to the switching of the valve.
An object of the present invention is to design a fuel pump for delivering fuel to an ejector and to an internal combustion engine so that the quantity and pressure of the fuel delivered to the internal combustion engine is independent of the fuel delivered to the ejector and so that the pump is easy to construct.
The object of the present invention is met by a pump having an outlet duct through which fuel is pumped to an internal combustion engine and a connection to an ejector for pumping fuel within the fuel tank, the pump having separate delivery chambers leading to the outlet duct and to the connection.
The fuel pump according to the present invention has, due to the separate delivery chambers, two mutually independent pumps arranged with a common rotor. The fuel pump according to the invention is simply arranged for the pressure and the quantity of the fuel to be delivered to the internal combustion engine by appropriate design of a first delivery chamber leading to the outlet duct. By this means, the internal combustion engine always receives the necessary fuel quantity and pressure. A second delivery chamber feeds the ejector and is separate from the first delivery chamber. The second delivery chamber may also be appropriately designed to deliver the necessary amount of fuel to the ejector. The present invention obviates the need for a valve for controlling the fuel delivered to the ejector or to the internal combustion engine. A further advantage of the invention is that fuel in the connection to the ejector flows in a particularly eddy-free manner, undisturbed by the valve of the known fuel pump. This allows a high fuel pump efficiency.
The fuel pump according to the present invention may be simply designed if the first and second delivery chambers respectively leading to the outlet duct and to the connection are concentrically arranged so that one surrounds the other. The length, diameter and position of the delivery chambers, for example, may be designed to meet the specified fuel pressure and the fuel quantity to be delivered.
It is possible to include separate inlet ducts for each of the delivery chambers so that the delivery chambers are like separate pumps. However, connecting the delivery chambers to a common inlet duct helps reduce the manufacturing costs of the fuel pump according to the present invention.
Mutual influence on the fuel flowing in the inlet duct to the two delivery chambers may be avoided by arranging a partition in the inlet duct extending from a fuel filter to the rotor so that the inlet duct on one side of the partition leads to the radially inner delivery chamber and the inlet duct on the other side of the partition leads to the radially outer delivery chamber. This partition may be provided during the manufacture of the pump housing or may be subsequently inserted in the inlet duct.
The ejector connected to the connection obtains a sufficient quantity of fuel for filling the surge chamber in the fuel tank if the delivery chamber leading to the connection is configured to be smaller than the delivery chamber leading to the outlet duct.
Compensation may be simply provided for the forces acting on the rotor if the connection and the outlet duct are located orthogonally to mutually opposite end faces of the rotor.
The rings of guide vanes may, for example, be arranged in the end faces of the rotor as in side channel pumps. The fuel pump according to the present invention may alternatively have a design which is particularly economical in space if the radially outer ring of guide vanes is arranged at the outer periphery of the rotor.
The guide vanes arranged on the outer periphery may, for example, extend over the whole height, i.e., axial length, of the rotor or may be arranged over the corner regions on the end faces as in the case of a peripheral pump. The cross section of the delivery chamber leading to the connection for the ejector may be particularly compactly designed if the radially outer ring of guide vanes protrudes from the outer periphery of the rotor in a partial region of its height and if the part-annular duct corresponding to the outer ring of guide vanes is configured in the manner of a groove.
To further reduce the manufacturing costs of the fuel pump according to the invention, the part-annular duct may be configured in the manner of a groove substantially arranged in one of the housing parts and is laterally bounded by the other housing part.
The fuel pump according to the present invention may comprise particularly small radial dimensions if the delivery chambers leading to the outlet duct and to the connection are arranged one behind the other viewed in the direction of rotation of the rotor, i.e., the circumferential direction. This design further reduces the manufacturing costs for the fuel pump according to the present invention, because the rotor then only requires a single ring of guide vanes.
The internal combustion engine and the ejector respectively receive the specified quantity of fuel if the first delivery chamber leading to the connection is shorter than the second delivery chamber.
Each of the delivery chambers could, for example, be connected by its own inlet duct to a fuel filter. To further reduce the manufacturing costs of the fuel pump according to the present invention, the inlet ducts leading to the delivery chambers may include a connection to a common fuel filter.
The connection of the fuel filter to the pump housing is of particularly simple design if the inlet duct branches within the pump housing to the individual delivery chambers.
To provide compensation for axial forces, the connection for the ejector and the outlet duct may be arranged on directly opposed sides of the rotor if the rotor includes one delivery chamber in the region of each of its end faces and if one of the delivery chambers is led to the outlet duct and the other of the delivery chambers is led to the connection.
During the initial filling of the fuel tank, only a small quantity of fuel is necessary for operating the internal combustion engine if the inlet duct of the delivery chamber leading to the connection of the ejector is provided for leading on into the fuel tank. This ensures that a small quantity of fuel in the fuel tank is available to the fuel pump, according to the invention, of the internal combustion engine after a short operating period.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.